Hydrazine is a colorless liquid, H.sub.2 NNH.sub.2, with a fish-like odor and a boiling point of 114.degree. C. Major uses of hydrazine include its employment for rocket fuels, as a corrosion inhibitor in boilers, and for the synthesis of biologically active materials such as plant-growth regulators. Exposure to vapors of hydrazine or vapors of a hydrazine derivative such as monomethylhydrazine is harmful to the human body. Even small concentrations of liquid hydrazine or certain hazardous derivatives of hydrazine can be harmful because of the ability of those substances to enter the body through the skin and attack internal organs. Vapors of those substances, even in low concentrations, are suspected of being carcinogenic. Consequently, in an environment where some persons may be exposed to the harmful vapors for different periods of time and to different vapor concentrations, there is a need for an inexpensive device for measuring each person's exposure to such vapors.
Few acceptable techniques are known for measuring a person's exposure to hydrazine or to hazardous derivatives of hydrazine. Of the few techniques that are now available, those that rely upon substances which change color when exposed to hydrazine lack the necessary sensitivity to low concentrations of hydrazine or its hazardous derivatives and most of the other techniques are either too cumbersome for use in personal monitoring or are not sufficiently reliable to enable a dependable evaluation of exposure to be made.